1. Field of Invention
This invention pertains to a flexible clutch for releasably coupling an axially rotatable driving shaft to a coaxial driven shaft.
More particularly, this invention pertains to a flexible clutch adapted to disengage an axially rotating driving shaft from a coaxial driven shaft when the driven shaft encounters resistance to rotation which is greater than the torque required for operation in a normal mode.
2. Description of the Related Art
In the field of pet doors it is generally desirable to provide a pet door which is lockable to prevent entry by animals other than the pets for which entry is desired, i.e. wild animals and pets other than those expected to have access to a house. One means for providing such a lockable door is to provide a door which is movable in a vertical direction into and out of a channel adapted to receive the outer edges of the door. When the door is engaged in the channel, it is prevented from pivoting about a horizontal axis. However, when the door is raised from the channel and thus released from the channel, it is free to pivot about a horizontal axis and allow free entry for a pet. One mechanism for effecting such vertical motion is to provide a selectively rotatable shaft which can be reversed in rotation to raise and lower the pet door by means of a gearbox.
One area of concern, however, is that a child may place a hand in the path of the door as it is driven into the channel. Alternatively, a pet may have a tail or paw in the path of the door as it is driven into the channel. Accordingly, it is desirable to provide a mechanism whereby the driving force to insert the door into the channel is reduced when the door encounters a resistive force which is greater than the torque required to insert the door into the channel in normal operation.